Telephone apparatus



Nov. 9 1926.

. E. H. SMYTHE TELEPHONE APPARATUS Filed Nov. 5. 1925 Mlle/7760K fdw/h /7.' .fmyf/re Patented 'Nov. 9, l gffi.

whit-TEE STATES manna EDWIN H. SMYTHE, OF CHICAGO, ILLINOIS, ASSIGNOR TO WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE AI'PARA'IUS.

Application filed November 5, 1925. Serial No. 66,951.

This invention relates to acoustic devices, and particularly to sound transmitting and reproducing devices employing large directacting diaphra ms.

The object ot the invention is-to provide means for automatically maintaining the adjustment of sound reproducing devices regardless of any permanent or temporary displacement of the center of the diaphragm due to contraction or expansion of materials, or to any other cause.

In accordance with the present invention a telephone sound transmitting or reproducing device of the loud speaking type is provided with means for maintaining a. constant relation between the center of the dia phragm and the electro responsive element regardless of any change in shape or dimensions of its members due for example to their contraction and expansion under variations in humidity and temperature.

In one arrangement a magnetic unit which has a large mass and preferably of the biased armature type is supported on vertical pivots remote from its center of the mass so as to ofier high impedance and 'remain substantially rigid to vibrations at frequencies of importance in music and. speech and still move readily with the center of the Referring'tothe drawings Fig. 1 is a plan view of a loud speaker embodying the invention, the diaphragm being broken away to show the magnetic upit; Fig. 2 is a detail side View of the magnetiounit of the inven-' tion; and Fig. 3 is a front View of the magnetic unit. v

For the purpose of illustration the invention is shown applied to a loud speaking receivcr of the cone type such as described and claimed in application Serial No. 690,803,

.filed February 5, 1924, for G. WV. Burchett,

wherein 5 represents the mounting for a double conical diaphragm 6 and the electromagnetic driving unit 7 which is connected to the apex of the diaphragm by a rod 8.

1Q provided with parallel ends 18 and 19 is secured to the magnet at a point remote from the center of mass of the unit by a strap 20 and a screw 21. The ends 18 and 19 of the bar16 are provided with recesses which engage the ends of" the bearing screws 13 and 14, respectively. These re cesses are preferably hemispherical and the ends of the screws 13 and 14 are correspondingly shaped so as to provide a large hearing surface tor introducing friction. The bar 16 may be made of resilient material so as to facilitate in adjusting and maintaining the pressure on the pivots. Lock nuts and 23 are provided for the pivot screws 1; and 14 for. locking them after adjustn'ient.

As in case of the receiver disclosed in the ll. L. \Vcgel application erial No. 635,107, filed April 30, 1923, to thcpoles of the mar net are attached polo pieces 26 and 28 between which an armature is supported at its mid-point by a resilient reed not shown.

A lever 24: is secured tofthe pole picceby ascrew 27 and its free end is connected to one end of the aru'iature by a r0d'25. At'a ill point intermediate the ends of the lever the diaphragm 6 is connected by the rod 8.

For the purpose of limiting the maximum movement of the magnet a screw 30 which secures ione of the pole pieces to the magnet is'extended through a hole 31 in the bracket 9 andtho end isprovided'withnuts i which act as stops. In shipping the unit these nuts may be turned down so as to rigidly. secure the magnet to the bracket. Under operating conditions the clearance between the stop nuts and the frame shouldbe such as to permit maximum movement" due to the contraction and expansion of the diahragm under changes of temperature an humidity.

radiating member,

. port maintaining the adjustment his provides a covenient arrangement Zen-automatically compensating for t e contraction and. the, 825531181011 and any permathe airgap between the armature and the pole pieces which is essential for the proper operation of sound reproducing devices. The magnetic system being quite massive and supported at a point remote from itsa very high lmpedance center of mass ofi'ers to vibrations at frequencies of importance in sound and speech reproduction. The friction the pivots-adds to this impedance in maintaining adjustment of the air gap. Since the axis ot the pivots is vortical, any displacement of the magnetic unit introduces no stresses in the Vibrator system. Should any stresses set up by t e expansion or the contraction of the diaphragm he insuiiicient to overcome the friction of the pivots, a state of equilibrium will be established as soon as operating current is applied and the diaphragm starts operating.

What is claimed is:

,1. In a loud speaking receiver having an actuating device of large mass, a large di- 'i'ect-acting diaphragm operatively associat'd with said actuating device and a supputt for said device, means connecting said deiiice and said support to permit relative movement therebetween whereby the oper ation of the dcv i ce is unaffected by expansionand ontraction of the diaphragm.

2.111 a loud speaking receiver, a sound an actuating member, a support for said members, and means intermediate one of said members and said supof said actuating member independent of the changes in shape of said radiating member.

In a loud speaking receiver, having a diaphragm, a balanced armature in operative relation to said diaphragm, a 'magnet and a support and ineans intermediate said suiport and said magnet maintaining the ba. ance of said armature independent'of the changes in shape of said diaphragm.

' t. In an acous ic device, having a large isplacement of the diapermanent adjustment conical dia hragm, a magnetic unit for driving sai diaphragm, and a support for said unit, a pivotal connection between said support and unit, said connection being remote from the center of mass of said unit.

5. In a sound reproducing device, having a diaphragm,

in humidity and temperature, said means comprising pivots supporting said magnet for movement-in a horizontal lane.

7. In a sound reproducing a large direct-acting diaphragm, an actuating device and a support common to both, means of securing said operating means at a point remote from its center of mass to said support for relative movement there to in' a horizontal plane whereby stresses due to the contraction and expansion, of said diaphragm are relieved by the displacement of said actuating device.

A sound reproducing device compris' ing a large direct-acting diaphragm, a per manent magnet,

a support common to said diaphragm and said magnet and vertical frictlon pivots remote from the center lot said magnet connecting it to said magnet, an armature, means resiliently supporting said armature in operative relation to said pole pieces, and means connecting said armature to said diaphragm.

In witness whereof, I hereunto subscribe my name this th day of October A. 1)., 1925.

EDWIN H. sM-r'rns,

an electromagnet, and a support common to said diaphragm and said evice having- 

